The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art to the present invention.
Photovoltaic cells convert optical energy to electrical energy and thus can be used to convert solar energy into electrical power. Photovoltaic solar cells can be made very thin and modular. The individual electrical output from one photovoltaic cell may range from a few milliwatts to a few watts. Several photovoltaic cells may be connected electrically and packaged in arrays to produce a desired amount of electricity. Photovoltaic cells can be used in a wide range of applications such as providing power to satellites and other spacecraft, providing electricity to residential and commercial properties, charging automobile batteries, etc.
In a conventional thin film solar cell, an electrode layer, a photovoltaic layer and another electrode layer are sequentially stacked. When the light enters the thin film solar cell from outside, free electron-hole pairs are generated in the photovoltaic layer by the solar energy, and the internal electric field formed by the PN junction makes electrons and holes respectively move toward two layers, so as to generate a storage state of electricity. Meanwhile, if a load circuit or an electronic device is connected, the electricity can be provided to drive the circuit or device.
The average photoelectric conversion efficiency of the current thin film solar cell is about 6-10% mainly due to a low light utilization rate. The light path of the light passing through the photovoltaic layer is limited by the thickness of the photovoltaic layer, so that the light is not effectively absorbed. Consequently, while photovoltaic devices have the potential to reduce reliance upon fossil fuels, the widespread use of photovoltaic devices has been hindered by inefficiency concerns and concerns regarding the material costs required to produce such devices. Accordingly, improvements in efficiency and/or manufacturing costs could increase usage of photovoltaic devices.